Molding compositions are useful in the electronics industry to encapsulate electrical components such as integrated circuit devices so as to protect them from electrical and environmental damage. Some of the essential features needed for current electronic packaging materials include low coefficient of thermal expansion, high thermal conductivity, low dielectric constant, low water absorption and low viscosity. If the thermal conductivity of the material composition is too low the encapsulant may itself be detrimental in that it may act as a heat barrier and cause the temperature of the electrical components to rise above the temperature reliability specifications for the components which, in turn, may shorten the useful life of the encapsulated electrical components particularly for components such as semiconductors.
The heat dissipation problem in microelectronics is becoming increasingly important as the demands for denser and faster circuits intensify. Polymer compounds having a high thermal conductivity are also useful for other products such as computer cases, battery cases, electronic controller housings and for other encasements where heat removal is an important consideration.
Applicant's parent patent application Ser. No. 08/846,457 discloses a composite polymer based material possessing the characteristics of low thermal expansion, high electrical resistivity and high thermal conductivity. The preferred polymer is a polybenzoxazine compound which is filled with particles containing boron nitride. Thermal conductivities as high as 37.5 W/mK were demonstrated based upon the loading concentration of the boron nitride filler. In general the higher the concentration of boron nitride the higher the thermal conductivity of the polymer composite. However, the viscosity of the composite also in creases in direct proportion to the increase in filler concentration. Beyond a certain filler loading, the increased viscosity will cause material processing problems. A molding compound must have adequate fluidity to enable it to be processed into product. Although additives and/or modifiers may be included to improve the flow characteristics of the molding compound they substantially increase cost and may affect other properties such as strength.